1. Technical Field
The present invention relates to a tool position compensation method, and more particularly to a tool position compensation method which, when a tool on a hand of an industrial robot is replaced, is capable of easily converting the position of a new tool based on the point data taught by the replaced tool.
2. Description of the Related Art
Industrial robots have found widespread use and are being used in many fields in recent years. As numerical control technology is advanced, more industrial robots are numerically controlled for improved operation. Multi-articulation robots have many axes, and are widely used in the welding process as they can perform a highly sophisticated operation.
FIG. 7 of the accompanying drawings is a perspective view of a general industrial robot which is an articulated robot having six axes. The articulated robot has a T-axis about which an arm assembly rotates, a W-axis about which a lower arm is tilted back and forth, a U-axis about which an upper arm is tilted vertically, an A-axis about which a wrist rotates in a horizontal plane, a B-axis about which the wrist moves in a vertical plane, and a C(.gamma.)-axis about which the wrist rolls, these axes being independently controlled. Designated at 1 in FIG. 7 is a base on which the articulated robot is supported. A T(.theta.)-axis servo motor 2 is mounted on the base 1 for turning the axes about the vertical axis (T-axis). On the T(.theta.)-axis servo motor 2, there is mounted a T(.theta.)-axis unit 3 rotated by the servo motor 2. A W-axis unit 4 is fixedly mounted on the T(.theta.)-axis unit 3, and a W-axis arm 5 is rotatably supported by a pivot shaft 5a on the W-axis unit 4, the W-axis arm 5 being operated by a W-axis drive mechanism 6. A U-axis arm 7 is rotatably supported by a pivot shaft 7a on the distal end of the W-axis arm 5, the U-axis arm 7 being operated by a U-axis drive mechanism 8. A wrist mechanism 9 is mounted on the distal end of the U-axis arm 7. The wrist mechanism 9 is rotated by an A-axis servo motor 10, vertically swung by a B-axis servo motor 11, and rolled by a C-axis servo motor 12. Desired operation is performed by a tool attached to the wrist mechanism 9. An articulated robot of the type described above is disclosed in Japanese Laid-Open Patent Publication No. 59-59371, for example.
A teach and playback robot control process has widely been used in which a tool is mounted onto the hand of a robot. In this process, the robot is manually trained by being moved through steps or points to store such points in a data memory in a control unit. The points can later be traced by the tool automatically. However, the training process is considerably difficult to effect. There are many types of tools available and points to be taught are different from tool to tool. Therefore, when a tool is replaced, the new tool has to be trained entirely, which is quite tedious and low in efficiency.